Air-insulated work station

ABSTRACT

A work station having a work space bounded by an air duct system. Air is sucked out of the ducts for filtering, part of the air being circulated downwardly through the work space and back to the ducts, and the remainder vented from the system. Air passageways adjacent to an access opening permit outside air to replenish the air in the ducts, the air flows established within the station serving to insulate the work space from gaseous communication with the outside atmosphere.

United States Patent [1 1 Eagleson, Jr.

[ July 22, 1975 AIR-INSULATED WORK STATION [75] Inventor: John M.Eagleson, Jr., Kennebunk,

Maine [731' Assignee: The Baker Company, Inc., Stanford,

Maine 22 1 Filed: Sept. 27, 1973 [21] Appl. No.: 401,196

[521' US. Cl. 98/115 LH; 55/D1G. 18 [51] Int. Cl. F23J 11/00; F24F 9/00[58] Field of Search 98/115 Ll-l, 115 R, 36; SS/DIG. 18, 473

[56] References Cited UNITED STATES PATENTS 2,886,124 5/1957 Scharmer98/115 K 3,301,167 1/1967 Howard et a1... 3,318,076 5/1967 Baker 98/115LH 1/1968 Taylor ct al. 98/115 LH 3,470,679 10/1969 Ramsey 55/4733,729,905 5/1973 Diccianni 98/115 LH 3,752,056 8/1973 Chamberlin et al98/1 15 LH 3,811,250 Fowler. Jr. 98/115 LH Primary Examine'r-Charles J.Myhre Assistant Examiner-Paul Devinsky 1 71 ABSTRACT A work stationhaving a work space bounded by an air duct system. Air is sucked out ofthe ducts for filtering, part of the air being circulated downwardlythrough the work space and back to the ducts, and the remainder ventedfrom the system. Air passageways adjacent to an access opening permitoutside air to replenish the air in the ducts, the air flows establishedwithin the station serving to insulate the work space from gaseouscommunication with the outside atmosphere.

8 Claims, 4 Drawing Figures llllilllllll' ill, fl l g H1"H1@ l 'l ll' JLll|lll lllllvvllvlrvqvlltllll lltllllllllllg PATENTEDJUL22|97s 3.895570SHEET 1 FIG 60 AIR-INSULATED WORK STATION BACKGROUND 1. Field of theInvention This invention relates to work stations having an enclosedwork space and an access opening thereto, and more particularly to suchwork stations that are constructed to segregate the work space from theambient atmosphere.

2. Description of the Prior Art I Various work stations have beendeveloped with the object of permitting the operator to insert his handsor instruments through an access opening into theinterior of a workspace. and at the same time to prevent contamination of the work spaceby outside gases or airborne particulates. Two approaches frequentlyfollowed have been blowing a continuous stream of air through the workspace and out the access opening, or circulating air down into the workspace, through openings in a lower work surface, and back up through thestation for re-entry into the work space, I

The first approach cannot be used if it is desired to fully segregatethe work space from the outside environment by preventing the passage ofuntreated gas in either direction between the two. With the secondapproach it is possible to seal off the access opening to the passage ofgas either into or out of the work space, but to accomplish totalsegregation, it has heretofore been necessary to surround the remainderof the work space with a completely gas impervious enclosure, with alljoints sealed by welding, gasketing, or the like. Even with suchconstruction, it is possible for cracks to develop, which if unnoticed,may endanger personnel in the area by permitting a leakage ofcontaminated gases from inside of the work station, or spoil thematerial within the work station by permitting entry thereinto ofambient air. In addition, a problem of gas leakage along the edges ofthe access opening has been encountered with many heretofore known workstations.

BRIEF SUMMARY OF THE INVENTION In view of the above-stated problemsencountered in the prior art, it is an object of the present inventionto provide a novel and improved work station having a work space that isinsulated from gas flows both to and from the outside atmosphere.Another object is the provision of a novel and improved work stationhaving a work space and an access opening permitting the introduction ofsolid objects into the work space, in which gas leaks through the accessopening and through the work station walls are effectively prevented. Afurther object is the provision ofa novel and improved work stationhaving a work space in which only non-contaminated air is permitted toenter the work space or to leave. the work station.

In the accomplishment of these and other objects, a work station isprovided, according to the present. invention, with a work space definedby bottom, side. and rear walls, each wall defining an air duct exteriorto the work space, and the bottom wall including a perforated worksurface. A front wall is also included, and has an opening providingaccess to the work space. A blower means takes in air from the air ductsand blows the air downwardly through the work-space. through theperforations (preferably distributed along the forward and rear portionsof the work surface). and back into the ducts for recirculation back tothe blower. Air passageways are also provided in at least one of theducts to admit outside air. The passageways are preferably distributedalong the forward edge of each of the side wall ducts, adjacent to theaccess opening, to inhibit gas leakage intoor out ofthe work spacethrough the access opening. Exhaust means are included to vent someofthe air in the ducts to the outside atmosphere, thereby establishing aflow of air into the ducts through the air passageways to replenish thevented air. Filter means are emplaced in the path of substantially allthe air impelled through the air ducts to remove airborne contaminantsbefore the air is either vented or blown into the work space. Any leaksof unfiltered gas are thereby captured within the ducts and delivered tothe filter means for decontamination.

The filter means preferably comprises a pair of filters, one disposed inthe path of air blown into the work space, and the other set in theexhaust means. According to another feature of the invention, the frontwall also defines an air duct exterior to the work space, with the twofilters acting on air contained in a plenum that is supplied by theblower means and surrounded by the blower means, the front, side, andrear air ducts, and the filters. By this means any gas leaving theplenum is either filtered or captured in the air ducts and returned tothe plenum. In a related feature a partition for the access opening isslideably lodged through a slit in an enclosure mounted on thefrontwall. Air passageways in the front wall provide a path for air inthe enclosure to be sucked through the front wall air duct and into theblower means, to filter outany impurities that may have entered theenclosure through the slit.

In a particular embodiment, the work station comprises an inner housingmounted within an outer housing and separated therefrom by an air space.The blower means is adapted to suck in air from the air space betweenthe two housings and to blow air downwardly through a work space definedby the inner housing, towards a perforated work surface. Air is ventedfrom the air space through an exhaust means, the vented air beingreplenished by outside air entering through air passageways in the outerhousing, and the remainder of the air in the air space being suppliedfrom the work space through the perforated work surface. Filter meansremove contaminants from the air prior to venting and entry into thework space. In this embodiment a plenum may be established by the blowermeans within the outer housing and above the inner housing, with a firstfilter disposed between the plenum and the work space and a secondfilter disposed between the plenum and the exhaust means.

The invention also comprehends the method of insulating a work spacecontained within a walledwork station from gaseous communication withthe atmosphere which includes bounding the work space with walls spacedinwardly from the work station walls, sucking out the air from the airspace between the work station and the work space walls, and filteringthe sucked air to "remove contaminates. A portion of the sucked air isvented from the work station, and the remainder impelled downwardlythrough the work space and returned to the air space, inducing the entryof atmospheric air into the air space to replenish the vented air.According to one feature of this method, air from the air space issucked into a blower means and then blown into a plenum above the workspace. A portion of the plenum air is vented from the work stationthrough a first filter, the remainder of the plenum air being admittedinto the work space through a second filter.

For the purpose of more fully explaining a preferred embodiment of theinvention, reference is now made to the following detailed descriptionthereof, together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a workstation constructed according to my invention, with a portion of thefront wall cut away;

FIG. 2 is a cross-sectional view of the work station in frontalelevation;

FIG. 3 is a cross-sectional view taken along the line 3-3 of FIG. 2; and

FIG. 4 is a fragmentary view of a corner of the work station showing theflow of air from the outside atmosphere and from the work space into airducts surrounding the work space.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIGS. 1-3, a workstation is shown having a generally rectangular outer housing with sidewalls 2 and 4, rear wall 6, and top and bottom walls 8 and 10,respectively. The housing is mounted on legs 12, which provide suitableleg space for the work station to be used while seated. A slideableglass partition 14, counterbalanced by a spring loaded steel tape (notshown), permits the interior of the station to be viewed, and can beraised to provide an access thereto. A fluorescent light assembly 16illuminates the interior of the station.

A work space generally indicated by numeral 18 is defined by an innerhousing having side walls 20 and 22', and rear and bottom walls 24 and26, respectively. A pair of one-third horsepower blowers 28 and 30,mounted above the inner housing, have an intake from the air spacebetween the inner and outer housings and are adapted to blow airdownwardly into a plenum 32, bounded in part by plenum walls 34. Afirst, elongate filter 36 of the high efficiency particulate arrestant(H.E.P.A.) type, designed to remove 99.99% of airborne particles .3microns or greater in diameter, is disposed between the plenum 32 andthe open top of the work space 18. An air diffuser 38 is mounted in thework space 18 below the filter 36 to distribute air coming down throughthe filter 36 from the plenum 32, and preferably produces a greater airflow rate at the forward and rear portions of the work space 18 than atthe central portion thereof.

The bottom wall 26 of the inner housing forms a work surface to supportmaterial placed within the work space 18. It is provided with a seriesof perforations 40, preferably distributed along the forward and rearportions of the work surface 26, permitting air blown into the workspace 18 to pass downwardly through the work surface 26 and circulateback through the air space between the inner and outer housings to theblowers 28 and 30.

A second H.E.P.A. filter 42 is set in a plenum exhaust opening 44 toremove particulates from air vented from the work station through theexhaust opening 44.

The inner and outer housing walls define a system of air ductssurrounding the portion of the work space 18 that is interior to thework station, the air within the ducts being sucked into the blowers 28and 30 and processed through the filters 36 and 42 when the statior isoperated. Air passageways are provided to admit out side air into theducts and thereby replenish the air vented from the station through theexhaust opening 44. Preferably the air passageways are distributed alongthe forward edge of each of the two volumetric side walls formedrespectively from inner and outer side walls 2 and 20, and from innerand outer side walls 4 and 22, the passageways comprising a series ofslots 46 adjacent to the sides of the access opening.

The glass partition 14 is slideably lodged through a slit 48 in anenclosure 50 that is mounted on the upper front wall 52 of the outerhousing, the partition 14 providing a unitary front wall for the innerhousing and the remainder of the outer housing. A plurality of airpassageways. preferably in the form of a series of slots 54 distributedalong the forward edge of each of the aforesaid volumetric walls,provide an air flow path between th'epartition enclosure 50 and an airduct defined by the upper front wall 52 in conjunction with the forwardplenum wall 34. Any air entering the enclosure 50 through slit 48, asthe partition is raised or lowered to respectively reveal or cover theaccess opening, is drawn through the slots 54 into the interior of thework station by the action of blowers 28 and 30. The plenum 32'itself isbounded by the plenum Walls 34, blowers 28 and 30, and the filters 36and 42, whereby any gas leakingthrough the plenum walls 34 enters theduct system and is sucked back into the blowers 28 and 30 and returnedto the plenum 32.

Frofn the above description it can be seen that the work space 18 isentirely enclosed by air ducts at its rear. bottom, and sides, filter 32at its top, and glass partition 14 at its front. The only direct pathfor gaseous flow between the work space 18 and the outside atmosphere isthrough the access opening when the partition 14 is raised. This flow iseffectively prevented, however. by the downward directed airstreamestablished within the work space 18 by blowers 28 and 30, which carriesthe gas just inside the access opening down through the work surfaceperforations 40 and into the air duct system, and by the intake ofoutside air intothe duct system through slots 46, which intake preventsgas leakage in either direction along the sides of the work space 18.Any gas that may leak into the air ducts either through the walls ofwork space 18 or from outside of the station. due to cracks or the likein the workstation walls, is sucked into the blowers 28 and 30 anddelivered to one of the filters 36 and 42 for decontamination. The workspace 18 is thereby completely insulated from gaseous communication withthe outside atmosphere by the various air flows established within-thework station. It has been found that the best contaihment is achievedwhen the ratio of the air mass traversing the work space filter 36 tothat vented through the exhaust filter 42 is about 3:1, and the air flowvelocity into the slots 46 is from about 50 to about 100 feet perminute.

Several control features are displayed on a control panel 56. Amagnehelic pressure guage 58 measures the pressure drop across the workspace filter 36. When the filter becomes dirty enough to increase thepressure differential and reduce the air flow velocity below the desiredlevel. the operator is notified by the guage needle crossing into amarked area on the guage to increase the blower speeds by adjustment ofcontrol knobs 60 for solid state speed controls. A constant rate of airflow may thus be obtained as the filter becomes dirty, therebyincreasing the filter life while maintaining a constant workingcondition. In addition, a warning light 62 is connected to light whenthe unit is in operation and the glass partition 14 is raised by morethan 8 inches, the access opening dimension that produces the best gascontainment efficiency.

The operation of the work station is best described with reference toFIGS. 24, in which arrows represent air flow. Air is sucked into theblowers 28 and 30 from all of the air ducts surrounding the work space18 and from the partition enclosure 50, establishing a less thanatmospheric pressure in the ducts. The air is blown into the plenum 32at an elevated pressure, from whence about 25% of the air is vented anddecontaminated through the exhaust filter 42. The remainder of the airis impelled through the work space filter 36 and formed by air diffuser38 into a substantially downward laminar flow with the majority of theair directed to the front or rear portions of the work space. Gasescontained within the work space are drawn by the airstream downwardthrough the work surface perforations 40 to the lower air duct, andthence upward principally through the rear duct and also through theside ducts back to the blowers 28 and 30, where the cycle is repeated.The vented air further reduces the pressure within the air ducts,producing an inflow of air through the slots 46 adjacent to the accessopening, into the side ducts, and up to the blowers 28 and 36.

The air ducts thus serve as a barrier between the work space and theoutside environment, any gas leaking into the ducts being sucked intothe blowers 28 and 30 and delivered to one of the filters 36 and 42before being introduced into the work space or vented from the unit. Theair flowing downward through the work space and into the intake slots 46also serves to seal off the access opening to gas flows in eitherdirection, while an operator is provided with convenient access to thework space when the glass partition 14 is raised.

While a particular embodiment of the invention has been shown anddescribed, there are modifications thereof which will be apparent tothose skilled in the art, and therefore it is not intended that theinvention be limited to the disclosed embodiment or the details thereof,and departures may be made therefrom within the spirit and scope of theinvention as defined in the claims.

What is claimed is:

1. An air-insulated work station comprising the combination of:

bottom, side, and rear walls defining a work space,

said bottom wall including a work surface for said work space, bafflescooperating with each of said walls to define air ducts exterior to saidwork space,

a front wall having an opening providing access to said work space,

blower means having an air intake from said ducts and adapted to blowair down into said work space toward said work surface, said ductsforming a return path to said blower means for air which has passedthrough said work space,

said work surface being perforated and at least one of said air ductsprovided with air passageways to admit air respectively from said workspace and from outside of said work station into said ducts, exhaustmeans adapted to vent some of the air in said ducts from said workstation, and thereby establish a flow of air from outside of said workstation through said air passageways and into said air ducts toreplenish the vented air, and

filter means in the path of air impelled by said blower means forremoving contaminants therein, said filter means intermediate saidblower means and both said work space and said exhaust means,

the air flow produced within said ducts serving to insulate said workspace from gaseous communication with the outside atmosphere resultingfrom leaks of unfiltered gas into said ducts, by passing substantiallyall the gas in said ducts through said filter means.

2. The work station of claim 1, wherein said air passageways aredistributed along the forward edge of each of the air ducts defined bysaid side walls.

3. The work station of claim 2, wherein air passageways are providedadjacent to said access opening to inhibit the flow of gas into or outof said work space through said access opening.

4. The work station of claim 3, wherein said blower means, exhaustmeans, and air passageways are adapted to produce an air flow velocityinto said air passageways of from about 50 to about feet per minute.

5. The work station of claim 3, and further including a partitionslideable between first and second positions respectively covering andrevealing said access opening, an enclosure for said partition mountedon said front wall, said partition slideably lodged in said enclosurethrough a slit in the lower portion thereof, said front wall defining anair duct exterior to said work space, said air duct providing an airintake to said blower means, and air passageways between said partitionenclosure and said front wall air duct, said blower means adapted toimpel gas in said partition enclosure through said air passageways andsaid front wall air duct and thence to said filter means.

6. The work station of claim 1, wherein said filter means comprises afirst filter disposed in the path of air blown into said work space anda second filter disposed in the path of air vented through said exhaustmeans.

7. The work station of claim 6, wherein said front wall defines an airduct exterior to said work space, said front wall duct providing an airintake to said blower means, and including a plenum supplied by saidblower means and surrounded by said blower means, filter means, and saidfront, side, and rear air ducts, whereby any unfiltered gas escapingfrom said plenum is returned thereto through said ducts by said blowermeans.

8. The work station of claim 1, wherein the perforations in said worksurface are distributed along the forward and rear portions of said worksurface, and including means to direct a greater air flow rate from saidblower to the forward and rear portions of said work space than to thecentral portion thereof, thereby inhibiting the flow of gas outwardly tothe front or rear from said central work space portion.

1. An air-insulated work station comprising the combination of: bottom,side, and rear walls defining a work space, said bottom wall including awork surface for said work space, baffles cooperating with each of saidwalls to define air ducts exterior to said work space, a front wallhaving an opening providing access to said work space, blower meanshaving an air intake from said ducts and adapted to blow air down intosaid work space toward said work surface, said ducts forming a returnpath to said blower means for air which has passed through said workspace, said work surface being perforated and at least one of said airducts provided with air passageways to admit air respectively from saidwork space and from outside of said work station into said ducts,exhaust means adapted to vent some of the air in said ducts from saidwork station, and thereby establish a flow of air from outside of saidwork station through said air passageways and into said air ducts toreplenish the vented air, and filter means in the path of air impelledby said blower means for removing contaminants therein, said filtermeans intermediate said blower means and both said work space and saidexhaust means, the air flow produced within said ducts serving toinsulate said work space from gaseous communication with the outsideatmosphere resulting from leaks of unfiltered gas into said ducts, bypassing substantially all the gas in said ducts through said filtermeans.
 2. The work station of claim 1, wherein said air passageways aredistributed along the forward edge of each of the air ducts defined bysaid side walls.
 3. The work station of claim 2, wherein air passagewaysare provided adjacent to said access opening to inhibit the flow of gasinto or out of said work space through said access opening.
 4. The workstation of claim 3, wherein said blower means, exhaust means, and airpassageways are adapted to produce an air flow velocity into said airpassageways of from about 50 to about 100 feet per minute.
 5. The workstation of claim 3, and further including a partition slideable betweenfirst and second positions respectively covering and revealing saidaccess opening, an enclosure for said partition mounted on said frontwall, said partition slideably lodged in said enclosure through a slitin the lower portion thereof, said front wall defining an air ductexterior to said work space, said air duct providing an air intake tosaid blower means, and air passageways between said partition enclosureand said front wall air duct, said blower means adapted to impel gas insaid partitiOn enclosure through said air passageways and said frontwall air duct and thence to said filter means.
 6. The work station ofclaim 1, wherein said filter means comprises a first filter disposed inthe path of air blown into said work space and a second filter disposedin the path of air vented through said exhaust means.
 7. The workstation of claim 6, wherein said front wall defines an air duct exteriorto said work space, said front wall duct providing an air intake to saidblower means, and including a plenum supplied by said blower means andsurrounded by said blower means, filter means, and said front, side, andrear air ducts, whereby any unfiltered gas escaping from said plenum isreturned thereto through said ducts by said blower means.
 8. The workstation of claim 1, wherein the perforations in said work surface aredistributed along the forward and rear portions of said work surface,and including means to direct a greater air flow rate from said blowerto the forward and rear portions of said work space than to the centralportion thereof, thereby inhibiting the flow of gas outwardly to thefront or rear from said central work space portion.